Automatic control apparatus



March 24, 1942; I c, 3 MOORE 2,277,131

- AUTOMATIC CONTROL APPARATUS I Filed Feb. 4, 1938 2 Sheets-Sheet 1 ENTOR.

AN B. MOORE March 24,1942. c; B. MOOF'QE 2,277,131

AUTOMATIC CONTROL APPARATUS Filed Feb. 4, 1938 2 Shgets-Sheet 2 A IINVENTOR. COL AN B. MOORE Patented Mar. 24, 1942 2.277.131 AUTOMATICCONTROL APPARATUS Coleman B. Moore, Carroll Park, Pa., assignor to TheBrown Instrument Company, Philadelphia, I Pa., a corporation ofPennsylvania l Application February 4, 1938, Serial No. 188,739

2 Claims. The general object of the present invention is to provideimproved control apparatus of the type comprising what may be called anair controller, by'means of which variations in a measurable controllingcondition produce predetermined changes in a pressure fluid, ordinarilyair under pressure, which thus forms a control force, which in magnitudeis a definite function of the controlling condition, and which may a beemployed directly, or more usually through a relay mechanism, to varysome controlled condition, which may or may not react upon thecontrolling condition. Such control apparatus has a wide range of use,as the controlling condition may be any condition, such as temperature,pressure or velocity, for example, constituting' or creating ameasurable force or action.

More specific objects of the present invention are to provideimprovements in the mechanism by which the fluid pressure control forceis regulated or varied in accordance with variations in the controllingcondition, those improvements being partly mechanical and of especialimportance from the standpoint of mechanical simplicity andefiectiveness, but also including novel provisions contributing to asensitive or quickly responsive regulatory action, and to a reduction inthe hunting tendency which sensitive regulatory'action ordinarily tendsto produce.

Still more specifically it is an object of the invention to providemeans whereby the control mechanism may be adjusted for particularrequirements of service. In fluid pressure actuated control apparatus ofthe type with which this invention is concerned, an element sensitiveto. a variable condition such as temperature, is adapted to varythepressure upon a fluid motor such as a fuel valve, governing thecondition such as temperature, or governing some related condition. Fordifierent processes the relation of condition change to correctiveaction sometimes referred to as the throttling range or sensitivity ofthe control'apparatus, is necessarily differents The present inventionprovides means for ready adjustment of this relation,

The various features of novelty which characterize my invention arepointed out with particularity in the claims annexed to and forming apart of this specification. For a better understanding of the invention,however, and the advantages possessed by it, reference should be had tothe accompanying drawings and descriptive matter in which I haveillustrated and described preferred embodiments of the invention.

Of the drawings:

Fig. 1 is a more 'or less diagrammatical view of one type of controlapparatus illustrating the invention;

Fig. 2 is another embodiment of the invention; I

Fig. 3 is a perspective view of the linkage mechanism shown in Fig. 1;and

Fig. 4 is a perspective view of the linkage mechanism in Fig. 2.

The particular form of control system diagrammatically shown by way ofexample in Fig. l, is adapted to adjust a fuel supply valve .or othercontroller a, to thereby regulate the supply of heat to a furnace A asrequired to maintain an approximately constant furnace temperature whichis measured by an expansion fluid thermometer of which B is thetemperature responsive bulb or chamber. The fluid pressure in chamber B,which increases and decreases as the furnace temperature rises andfalls, is transmitted by a conduit b to a pressure responsive element C,shown as a Bourdon tube of helical form having its stationary endconnected to the conduit b, and having its movable end secured to an armC, which is pivoted to turn about an axis C clockwise orcounter-clockwise, as the pressure in the tube rises or falls.

Through suitable connections, the oscillations of the arm C give motionto the valve :1, which, as shown, forms a part of a control pressureregulator or air controller unit D, and regulates.

the escape of air from, and thereby regulates the control air pressurein the regulator chamber D. The latter receives air through a pipe H,and a restriction H. The pressure in the chamber D is transmitted byconduit Do to the chamber a of the fuel valve a.

All the above-mentioned parts, except the furnace A, valve 11 and bulbB, are advantageously combined in a control instrument, which as shownin Fig. 2, may well be a recording meter similar in general form to acommercial type of meter used for recording temperature and pressure.drical casing I having an upper segmental partition wall I adapted tocooperate with a lower segmental partition wall 13, to cover the frontof the casing and support a chart and chart driving motor notshown. Thefront of the instrument may be covered by a bezel not shown.

The meter'pen or indicating pointer is carried by an element K pivotedto oscillate about an axis K The major portion of the element K is backof the wall ll but an arm portion K extends through a wall slot 1 Anormally adjustable index L may be set, to indicate the nor- Such ameter -may include a cylinstruction illustrated, comprises a cup-shapedcasing body forming the cylindrical outer wall and one end wall of thechamber D. The open end of the casing body is normally closed by an endI head D removably attached thereto. The bleeder outlet D from thechamber D controlled by the valve (1 is formed by the axial. passage ina bolt-like nozzle member D threaded through an opening in the head D"and having its enlarged outer end rounded to form a convex surfaceracing the valve d and the annular portion of which immediately adjacentthe passage D forms a seat for the valve d. The latter is in the form ofa thin plate or bar which extends generally parallel to and diametrallyof the end head D", with one end in front of the nozzle part D which islocated adjacent one side of the end head. The end of the valve member dremote from the nozzle D is pivotally connected to the end head D. Asshown the pivotal connection comprises spaced apart transverseprojections d from the valve member d, and a hinge shaft d passingthrough those projections'and through hinge lugs 11 carried by the endhead D". I

The operating connections for the valve member d include a bell cranklever M. As shown,

the 'lever M is carried on a pin M carried by a second bell crank leverMA. Lever MA is pivoted atd andisconnectedbyalinkEto alinkMN attached toabutment N, the, purpose of which is later described. Bell crank M isconnected by a link KD with .the control point setting device L and thepen K. Lever M is provided with a pin M adapted to engage the under sideof valve d, and at times carry the latter away from the nozzle D againstthe action of spring d", which tends to move the valve toward thenozzle. This, in efiect, gives a pivotal connection between the valvemember d and the lever M.

The link KD is pivotally connected to a lever K pivoted at KL to agenerally horizontal arm L of the control point setting index L. A linkL is pivoted at one end to member L and at its other end to rotatablemember L whereby manual rotation of the latter will vary the. positionof pivot point KL, and simultaneously adjust the index L to indicate thecondition value to be maintained. Lever K is rotated about pivot KL bymeans of link K to which it is attached, when the arm K attached to penK and also attached to link K is rotated by the temperature responsivearm C. Thus upon movement or arm C, the link KD will be raised orlowered accordingly.

As the element K rotates clockwise or counterclockwise in response to anincrease or decrease I of pressure in the Bourdon tube C, the lever M vchamber D. a

For purposes hereinafter explained, the abutment N is not stationary butis moved toward and away from the valve member 12, following and as aresult of an increase or decrease respectively 7 in the pressure in thechamber D. The abutment N is so moved as a result of the variations inthe air pressure acting on the outer side of a bellows element 0 whichis axially disposed within the device D and of which the abutment Nforms a movable end wall. The end of the bellows element 0 remote fromthe abutment N is anchored to the end head D The interior of the bellowsis in free communication with the; atmosphere through thecenter openingd in the end head atmosphere through a passage d in the end wall I D,the rate of air flow through said passage being regulable. The meansshown for regulating the flow through the passage (1 is in the form of agrooved screw obturator d threaded into the out- -er end of the passage,and throttling the latter more or less, according to the extent to whichit extends into the passage.

Each of thebellows elements 0 and P has longitudinal resilience. Inconsequence each bellows has a definite length when the pressures actving on its inner and outer walls are the same. when those pressures areunequal, the extent to which the bellows is contracted if the externalpressure exceeds the internal pressure, or is elongated if the internalpressure exceeds the external pressure, is that required to make thediflerential of the internal and external pressures acting on thebellows, equal to the opposing resilient bellows force which resultsfrom the contraction or elongation of the bellows; said resilient forceof itself always tending to return the bellows to its normal orunstressed length.

On an increase in the pressure within the Bourdon tube C and aconsequent movement of the part K in the clockwise direction, the valved is moved by a corresponding distance away from the nozzle D therebyreducing the pressure in D. The pressure reduction in D elongates thebellows P. The first eifect of its elongation is to enlarge theinter-bellows space OP and to reduce the pressure in the latter owing tothe relatively slow inflow of air permitted by the restricted passage d.The reduction in pressure in OP elongates the bellows O. The resultantmovement of the abutment N away from the end head D moves the valve dback toward the nozzle D through lever and link mechanism laterdescribed, thereby tending to increase the pressure in chamber D. Inpractice the mechanism is so proportioned and adjusted that the effecton the pressure in D of a change in position of the part K is onlypartially neutralized by the efiect of the pressure change on the lengthof the bellows O. The decrease in pressure in chamber OP produces aninflow of air through the passage 11 which tends to slowly bring thepressure in chamber OP into equality with the pressure of theatmosphere. As the pressure in the chamber OP builds up, the bellows Oshortens and thereby moves the valve d away from the nozzle D and backtowards the position into which it was moved on the original change inposition of the part K provided the latter remains stationary in themeantime. The converse of the actions just described occur on a decreasein the pressure in the Bourdon tube C and a corresponding adjustment ofthe part K in the counter-clockwise direction.

While the adjustment at any timeof the valve mechanism comprising theport or passage D and member d. depends on the relative positions at thetime of the parts K and N, the position and movement of eachof thoseparts is independent of the position of the other. It is to be noted,moreover, that the apparatus is so proportioned that the repulsiveeffect-on the valve d of the air flow through the port D" is too smallto have any significant effect on the positions and movements of eitherof the parts K, and N.

From what has just been said, it will be apparent that the first effectof' a change in the controlling condition and corresponding change inthe part K is to produce a corresponding initiaTchange in pressure inthe chamber D. This initial change in pressure in the chamber D isautomatically followed by a smaller reverse chang'ein pressure, astheinitial ch e is a reversal of direction of the change'in the controllingcondition and the control apparatus may be adjusted so that thecorresponding initial adjustment of the control valve a is quick enoughand great enough to produce a substantial corrective effect withoutgiving rise to such a hunting difficulty as would exist but for theautomatic reverse change in pressure in the chamber D.

If it be assumed, for example, that an initial clockwise change of theposition of the part K occurs as a result of an increase in temperaturedue to a decrease in furnace load which continues for some time so thatless fuel is needed than was previously required, said change may wellproduce a temporarily excessive initial decrease in pressure in chamberD, such that, if maintainedfuel wouldhesupplied to the furnace moreslowly than required to continuously meet the then existing demand onthe furnace for heat. The extent of this decrease in pressure in D isgauged by the movementgiven thevalve'fi by the expansion of the bellows0, occurring as a result of suchdecrease. Such initial excess in fuelreduction tends quickly to arrest the rise of the furnace temperature,and to decrease that temperature. As the furnace temperature falls, thelever K turns counter-clockwise and the tendency to an excessivedecrease in that temperature is neutralized more or less by anaccompanyirig increasein pressure in the chamber D, resulting from themovement given the valve d by the counter-clockwise motion of lever Kthe magnitudeoLthe-increase being gauged by the compression of bellows Ooccurring as a result of such increase. The subsequent slow compressionof the bellows O, as the-pressure in the chamber OP approaches equalitywith that of the atmosphere, again tends to decrease the fuel supply tothe furnace, but unless the furnace load has become still smaller in themeantime, the effect onnposition of the valve d of such compression ofthe bellows 0 will be partially neu tralized by the decrease in thefurnace temperature and resultant counter-clockwise change in positionof the part K If'the demand on the furnace for heat does not changeafter the bellows 0 has co tracteetcrnmriwordnnexed length, the valve dwill come to rest with the part K in a position corresponding to afurnace temperature slightly higher than would exist in a stableoperating condition with a larger demand on the'furnace for heat.

The means through which the movements of abutment N effect follow upmovements of the valve d are important from the standpoint of ease ofadjustment in the field, since ordinarily such adjustment is madeexperimentally while the instrument is in service dependent upon theprocess requirements. To facilitate this adjustment commonly termed thethrottling range" adjustment, I do not connect the link MN directly tothe lever -MA but provide adjustable linkage therebetween by means ofwhich the ratio of movement of abutment N to the movement of lever MAmay be varied. Since this ratio 'F which is journalled in the instrumentframework at F, and pivotally carries at G one end oi a link G. Theopposite end G of link G pivotally supports the link MN and by virtue ofthe freedom of the latter to pivot at N, the path of movement of thepoint (It will be circularly about G in any adjusted position of thelever F. Lever F is frictionallyheld in any position to which it may beadjusted by a" friction disc F The path of lever MN will thus determinethe amount of movement, resulting 'from a given movement of abutment.N,,which will be imparted to lever MA through link E attaciied to linkMN at E and to lever MA at E as will be clear: When lever F is in thefull line position of Fig. 1, in which the axes of pivots F and G arealigned and links G and E are at right angles, the movement of lever MAin response to a given move ment of link MN will be-maximnm. Thatmovement will-belrQ when the lever F is adjusted toward the dotted lineposition of Fig. 1, and into the position in which links G and E areparallel. From the foregoing it will be clear that following a pressurechange in chamber D as a result of a movement of lever K and valve d, apartial neutralization will ta'ke placeas a result of the movement ofabutment N, and y'an amount dependent upon the adjustment of lever .F,which is termed the throttling range adjustment. A scale GT suitablycalibrated and with which index F on lever F cooperates, may be providedto facilitate adjustment of the throttling range.

in Fig. 2 is illustrated an embodiment of the invention which is moresimple than the device of Fig. 1 in respect to the normal controlfunctions. The corresponding reference letters of Figs. 1 and 2 indicatelike parts, while the letters d n, n, mn, e, e ma, m, m, f, g, g, and gof Fig. 2 indicate parts equivalent in general purpose to the parts D,N, N, MN, E, E MA, M, M, F, G, G, and G of Fig. 1. In Fig. 2, however,there are no elements corresponding to the bellows P, and obturatorparts (1 and d and the corresponding control function attained withtheuse of those-parts is*not"attained with the apparatus of Fig. 2. Theomitted function namely, compensation or reset for load varia: tions, isunnecessary or undesirable for the purposes for which the apparatus ofFig. 2 is intended, but the throttling range adjustment means is equallyapplicable to this form. of regulator. In this form the nozzle it neednot communicate directly with the chamber D as does the nozzle D of Fig.1, thoughfundamentally it may, but is adapted to be connected to .anintermediate booster air relay which in turn may be connected to chamberD to govern the pressure therein. On a movement of valve d the pressurein nozzle d is changed proportionally changing the pressure in chamberD', whereby bellows O is expanded or contracted against the normalbellows resiliency tending to maintain a given length, which may besupplemented by opposed springs A and OB. Corresponding movements arethereby given link mn, pivoted at n, to abutment n, in a path determinedby the link a, pivoted to link' mn at g and to relatively fixed lever fat g r The. lever f is adjusted by a spur gear and segment arrangementwhereby the pivot g is positioned. The links e and g are pivoted to thelinkmnat a common point 9 so that when the adjustment of lever f is suchas to align the axes of pivots e andg, no movement of lever ma resultsfrom themovement of link mn. When pivots e and g, are displaced however,lever ma will be moved by link mn, on a movement of the latter, by anamount depending upon the path of pivot g which is constrained to moveabout pivot g as a center.

on the plate IB adjacent the window IE to cooperate with a dial, visiblethrgugh the 'window and carried by the adjusting 'ineans for lever 1,whereby a calibrated'adjustment of the throttling range can be made.

It is noted that my throttling range adjustment is useful in a device inwhich no follow up action such as is effected by bellows O, is employed.In operating a simple air controller with no such action, a connectionis usually made from a member responsive to the condition directly tothe control member or valve d. If in a -the deyice,of Eig, glor example,the bulb b is considered as connected to the pipe Da, the

of my invention asset forth in the appended claims, and that certainfeatures of my invention may sometimes be used to advantage without acorresponding use of other features.

Having now described my invention, what I claim as new and desire tosecure by Letters Patent is: 1. In a pneumatic control device, anelement deflectable in accordance with changes in a measurablecondition, a nozzle supplied with air under pressure and communicatingwith pressure responsive means controling said condition,

a movable member adapted to cooperate withsaid-nozzle to efiect controlof said condition proportionately to its position, means including afloating lever connecting said element and member for movement of thelatter by said element, means adapted to partially neutralize thepressure change resulting from'a movement of said member including apart responsive to said pressure change and a connection between saidpart and member including a link pivotally attached at one end to saidpart, a'second link, a ratio adjustingmember supporting one end of saidsecond link, a connection between the second ends of said two linksadapted to constrain movement of said first link through a pathdepending upon the position of said ratio adjusting member, and a thirdlink pivoted to said first link at a point between its connection tosaid pressure responsive part and said second link and operative toconnect said first link and floating lever to move said member bymovement of said first link.

2. In a control device, an element deflectable in accordance withchanges in a measurable con dition, a movable member adapted to eflectcontrol of said condition proportionately to its position, meansincluding a floating lever connect- Bourdon tube 0 and associatelinkCK'afidpenIoingiaidelement and member for movement of K omitted, andlink K made stationary, variation in temperature in the furnace willadjust valve d through link mn thereby varying the pressure in pipe DA,which in this case would be directly connected to the valve aindependently of chamber D. Adjusting means L may then be used todetermine the value of the condition to be maintained, the link KDacting on one arm of lever m solely for that purpose and the link mnacting on anotherarm of lever m in response to the measured condition.In the various forms I consider the lever F or f as' a ratio adjustinglever.

the latter by said element, means adapted to partially neutralize thecontrol effect of said -movement of said link for a given movement ofsaid second element comprising a part to movably support the outer endof said'link, an adjustable support for said part whereby as theposition of the support is changed the part will constrain said link formovement through ditierent paths, a second link, pivoted tosaid flrstWhile in accordance with the provisions 6f link between its points ofconnection with said the statutes, I have illustrated and described theseconTieTeinentand said part, and a lever moved best form of myinvention now known to me, it will be apparent to those skilled in theart that changes may be made in the form of the apparatus disclosedwithout departing from the spirit COLEMAN B. MOORE.

